Much attention has been focused on the use of 4H-type silicon carbide (SiC) with a wide band gap as a material for semiconductor elements in place of silicon (Si). 4H-type silicon carbide has a higher breakdown voltage than silicon. As a result, a high breakdown voltage element can be formed with the use of 4H-type silicon carbide.
However, when silicon is used as a semiconductor material, the built-in potential of a p-n junction is approximately 1 V, whereas, when 4H-type silicon carbide is used as the semiconductor material, the built-in potential of a p-n junction is approximately 3 V. As a result, the on-voltage of a built-in diode is approximately 3 V in a MOSFET made with 4H-type silicon carbide. Consequently, there is an increase in the conductive loss of the built-in diode. Moreover, a pn diode composed of 4H-type silicon carbide has a property in which energy released from the recombination of carriers converts the dislocations existing inside the SiC crystal into pairs of partial dislocations and generates stacking faults. As a result, the device characteristics may deteriorate when using 4H-type silicon carbide as a semiconductor material.